中亚热带米槠人工林土壤微生物残体碳对凋落物和根系碳输入的响应

Response of soil microbial necromass carbon to litter and root carbon inputs in a mid-subtropical Castanopsis carlesii plantation

微生物残体碳(MNC)是稳定土壤碳库的重要来源,探讨亚热带森林土壤微生物残体碳对地上(凋落物)、地下(根系)碳输入的响应对评估全球生态系统土壤碳贮量具有重要意义。本研究以福建三明森林生态系统国家野外科学观测研究站的米槠人工林为对象,设置去除根系(NR)、去除地上凋落物(NL)、无凋落物输入(即去除地上凋落物和地下根系输入,NI)、添加双倍地上凋落物(DL)4个处理,以无处理为对照(CK),7年后采集0~10 cm土层土壤样品,探究凋落物和根系输入变化下MNC含量及MNC对土壤有机碳贡献的变化特征。结果表明:1)与CK相比,NR处理下MNC、细菌残体碳(BNC)和真菌残体碳(FNC)分别降低了15.9%、20.2%和14.5%,其他处理无显著变化。2)与CK相比,NR、NL、NI和DL处理未对BNC、FNC和MNC的土壤有机碳贡献率产生显著影响。3)相关性分析和路径分析结果显示,植物碳输入变化通过改变土壤中的底物有效性和微生物群落结构直接或间接改变了土壤中微生物残体碳的含量。表明在维持中亚热带人工林土壤MNC方面,根系输入碳比地上植物来源碳更重要。

Microbial necromass carbon(MNC)is a crucial source for stable soil carbon pool,and understanding its response to carbon inputs from both aboveground(litter)and belowground(roots)in subtropical forest soils is essential for assessing soil carbon stocks in global ecosystems.In a Castanopsis carlesii plantation at the Sanming Forest Ecosystem National Observation and Research Station in Fujian Province,we conducted an experiment with five treatments,including root removal(NR),aboveground litter removal(NL),no litter input(removals of both aboveground litter and roots,NI),double aboveground litter addition(DL),and control(CK).After seven years,we collected soil samples in the 0-10 cm soil layer to examine changes in MNC content and its contribution to soil organic carbon(SOC).Results showed that NR treatment reduced MNC,bacterial necromass carbon(BNC),and fungal necromass carbon(FNC)by 15.9%,20.2%,and 14.5%,respectively,while other treatments did not induce significant changes.The NR,NL,NI,and DL treatments did not affect the contributions of BNC,FNC,and MNC to SOC.Correlation and path analyses revealed that litter and root carbon input treatments could alter the MNC content directly or indirectly through changing soil available substrates and microbial community structure.Our results suggested that roots exert a stronger influence on the maintenance of MNC than aboveground carbon source in the mid-subtropical plantations.